1. Field of the Invention
The present invention relates generally to microwavable containers for food products, and methods of fabrication thereof. The present invention relates more specifically to a microwavable tub for storing, shipping, heating and serving food products such as, for example, popcorn, puffed cheese snacks and pork rinds.
2. Description of Related Art
The increasing popularity of microwave cooking has lead to the development of several types of containers for microwave heating of food products. For example, a number of bag-type containers for microwave popping of popcorn are available. These containers are typically formed of paper or other flexible materials, and often include heating elements of microwave interactive susceptor material that absorb microwave energy to generate heat, which pops the popcorn. Such containers are typically shipped and stored in a folded configuration and, upon heating and popping of the corn, unfold into an expanded configuration.
More rigid containers have also been developed, such as cup-shaped containers for microwave heating of popcorn. These containers typically are in the form of generally frustoconical paperboard tubs. A microwave susceptor is installed on or around the floor of the tub, and a quantity of unpopped corn and cooking oil or shortening is placed in the tub""s interior. A plastic film or other barrier material is often applied over the corn in an effort to seal out external contaminants, seal in moisture, and preserve freshness. It has been found, for example, that moisture loss from popcorn inhibits popping and reduces popped volume. Efforts to form a hermetic seal around the food product in previously known containers have proven less than fully satisfactory. For example, one previously known container provides a concave cooking tray formed of coated paperboard stock for containing the food product and heating through microwave absorption. The tray includes a number of folds or corrugations, which present discontinuities in any seal attempted to be formed with a barrier material. These discontinuities form air channels that allow moisture loss from the food product. In an attempt to overcome this problem, a moisture impervious liner has been provided around the exterior of the tray, which liner is sealed to the barrier film around the lip of the tray. The multiple components required in previously known containers, however, typically results in increased costs of materials and assembly. Another disadvantage found to inhere in previously known containers incorporating a tray for containing the food product is the potential for the food product to be displaced inadvertently from the tray onto the shelf or ledge formed by the lip of the tray, removing the food product from thermal contact with the microwave susceptor material, often resulting in incomplete cooking or popping.
Previously known paperboard tub containers for microwave cooking are typically assembled by depositing the food product onto the floor of an upright container, or into a heating tray placed within the container, and then installing liners and/or film in various configurations in an attempt to form a seal around the food product. As discussed above, the provision of cooking trays and liners undesirably increases expense and may adversely affect cooking performance. If the food product is distributed across the container floor, attempts to form a seal around the food product by sealing a cover film to the container walls typically are unsuccessful, as moisture may escape through the walls and floor of the container, and/or through the seam between the walls and floor.
Thus it can be seen that a need exists for a container for microwave cooking of food products, which overcomes disadvantages of previously known containers. A need further exists for an economical and efficient method of fabricating a microwavable container for food. It is to the provision of a container and method of fabrication meeting these and other needs that the present invention is primarily directed.
The microwavable container and method of assembly of the present invention provide a number of improvements over previously known containers and methods of assembling such containers. For example, the container of the present invention prevents moisture loss and contamination by means of a simplified hermetic sealing arrangement described in greater detail below. This sealing arrangement results in a fresher food product, thereby enhancing consumer enjoyment. Shelf life of the product is also extended. The simplified sealing arrangement reduces material and assembly costs, resulting in a more commercially viable product. The container is easy and convenient for consumers to use, has an attractive shelf appearance, is nestable for ease of shipping and handling and reduced shelf space requirements, and provides large visible surface areas for the display of point-of-sale marketing features.
Briefly described, one aspect of the present invention provides a container for microwave heating of a food product. The container preferably includes a substantially upright sidewall assembly defining an interior volume, the sidewall assembly having a base, a mouth and at least one wall panel extending between the base and the mouth. The container preferably also includes a moisture-impervious floor extending from the at least one wall panel adjacent the base. The floor has an interior face defining the lower extent of the interior volume and an exterior face opposite the interior face. The container preferably also includes a sheet of barrier material forming a pocket for containing a food product, the sheet of barrier material being continuously sealed to the interior face of the floor around the pocket.
In preferred embodiments, the container of the present invention includes a generally rectangular tub assembly having four wall panels. Alternatively, the tub assembly can be a generally cylindrical or frustoconical tub having one wall panel closed upon itself. The tub assembly of the present invention can be fabricated from paperboard blanks folded and assembled in manners described in greater detail below. The floor of the container comprises a moisture barrier, preferably provided on the interior face of the floor to prevent migration of moisture into or through the floor material. The floor preferably, but not necessarily, also comprises a microwave susceptor material to enhance heating of the food product. The microwave susceptor material is preferably disposed to the interior face of the floor, but can be disposed to its exterior face or be formed integrally with the floor. The microwave susceptor and the moisture barrier can be one and the same through appropriate material selection, or can be separate materials or layers functioning in combination. The at least one wall panel preferably slopes outwardly from the base to the mouth, whereby multiple containers can be nestably stacked.
In another aspect, the present invention provides a container for microwave heating of a food product, the container preferably including a generally polygonal tub having three or more generally flat wall panels, a moisture-impervious floor and an open mouth. In a further preferred embodiment, the tub is generally rectangular, having four wall panels. The container preferably also includes a sheet of barrier material, such as a moisture-impervious balloon film, forming a pocket for containing a food product, the sheet of barrier material being continuously sealed to the floor around the pocket. Support legs preferably extend below the floor from corners defined by the intersections of adjacent wall panels, the support legs being separated by notches formed by removal of portions of the wall panels. A microwave susceptor is preferably disposed to the floor, and may be disposed to the interior or exterior face of the floor, or be integrally formed with the floor. The wall panels preferably slope outwardly from the support legs to the mouth of the tub, whereby multiple containers can be nestably stacked.
In yet another aspect, the present invention provides one or more cooperating paperboard blanks for forming a container for microwave heating of a food product. In a preferred embodiment, a sidewall blank is provided having three or more wall panels, and more preferably four wall panels, adjacent wall panels joined along score lines for folding to form a sidewall assembly. A floor blank is also provided, having edges adapted to be attached to a respective wall panel of the sidewall blank. The floor blank preferably is formed from a moisture-impervious material and optionally includes a microwave susceptor.
In another aspect, the present invention provides a container for microwave heating of a food product, the container including a tub having at least one wall panel and a floor providing a moisture barrier. The container further includes a sheet of barrier material deformed to comprise a pocket for containing a food product, the sheet of barrier material sealed to said floor about the periphery of the pocket. The floor of the container preferably also includes a microwave susceptor to enhance heating performance.
In another aspect, the present invention provides a container for microwave heating of a food product, the container including a sidewall assembly having a base, a mouth, and at least one wall panel extending between the base and the mouth. The container further includes a floor extending horizontally from the at least one wall panel adjacent the base, the floor having an interior face and an exterior face and the at least one wall panel having an interior face and an exterior face as well. The container also includes a sheet barrier material, which cooperates with the interior face of the at least one wall panel and the interior face of the floor to form a volume for containing the food product. The sheet of barrier material is sealed to the interior face of the at least one wall panel.
In still another aspect, the present invention provides a method of assembling a container for microwave heating of a food product. The method preferably includes forming a pocket in a sheet of barrier material, depositing a quantity of a food product within the pocket, placing a tub assembly having a floor and at least one wall panel over the food product, and sealing the barrier material to the floor of the tub assembly around the pocket to encapsulate the quantity of food product between the barrier material and the moisture-impervious floor of the tub assembly. In a further preferred embodiment, the barrier material is a moisture-impervious film, and the sealing step of the method is preferably carried out by heat sealing the sheet of moisture-impervious film to the floor of the tub assembly. Preferably, the heat seal is formed by applying heat from the outside of the container, through the paperboard or other material of construction of the tub assembly. The forming step can be carried out by deforming the barrier material as with a mandrel and die, vacuum forming, heat forming, folding, crimping, and/or through the provision of a preformed pocket. Heat can be applied to the sheet of barrier material during the forming step, as through the use of a heated vacuum platen, to plastically deform the material. The method may further include attaching the barrier material to a wall panel of the tub assembly at one or more locations.
In another aspect, the present invention provides a method of assembling a container for microwave heating of a food product, the method entailing fabricating a tub assembly by folding at least one blank to form a floor and at least one wall panel, forming a pocket in a sheet of barrier material, depositing a quantity of a food product within the pocket, inserting at least a portion of the barrier material within the tub assembly whereby the pocket of food product is adjacent the floor of the tub assembly, and forming a continuous seal between the barrier material and the floor of the tub assembly around the pocket.
In another aspect, the present invention provides a method of hermetically sealing a food product within a microwave cooking container, the method entailing depositing the food product between a sheet of barrier material and a moisture barrier portion of the container, and forming a continuous seal between the barrier material and the moisture barrier portion of the container.
These and other features and advantages of preferred forms of the present invention are described herein with reference to the drawing figures.